The power supply system including multiple power supplies connected in parallel requires balancing of load currents in the power supplies in operation. In this respect, many proposals have been made for methods of balancing the load currents (For example, see Patent Literature 1 and 2).
In addition, Patent Literature 3 and 4 disclose power supply systems in which the number of power supplies in operation is changed depending on the load current so as to enhance conversion efficiency.
In these power supply systems, a load current ITOTAL of a power supply system is divided by a maximum rated current IOMAX in individual power supplies, the result of the division is rounded up, and the value thus obtained is determined as the number of required power supplies in operation. According to this scheme, when the load current (an average value) of the power supplies in operation reaches the maximum rated current IOMAX, the number of power supplies in operation is increased by one.